Recovery of waste heat in water gas operations



July 17, 1934. F. w; STEERE RECOVERY OF WASTE HEAT IN WATER GAS OPERATIONS Filed Nov'. 17', 1928 ATTORNEY i atentecl July 17, 1934 UNITED STATES PATENT OFFICE RECOVERY OF WASTE HEAT IN WATER GAS OPERATIONS Application November 1928, Serial No. 320,089

6 Claims.

This invention relates to the recovery of heat from industrial gases and particularly to a method of supplying the steam required in the operation of water gas sets in an economical manner by utilizing waste heat which is normally discharged with the stack gases.

In the production of Water gas and blue water gas, carbonaceous fuel is heated to incandescence and is thereafter subjected to the action of steam. The initial period during which the temperature of the carbonaceous fuel is raised is ordinarily. referred to as the blow. I The gasmaking period is usually called the make and may be divided into up-run and back-run cycles.

The steam which is supplied during the make is derived ordinarily from boilers which are operated for that purpose, or it may be exhauststeam from other sources. sary to provide boilers and to operate them at considerable expense, in order that the required amount of steam may be available.

Attempts have been made heretofore to utilize a portion of the waste heat in so-called waste heat boilers, through which the stack gases are conducted during the blow period. Such boilers are expensive to install and to maintain. As a substitute for waste heat boilers, a flash boiler has been suggested in which water is sprayed upon surfaces previously heated by contact with the hot stack gases. The flash boiler is, however, subject to the objection that the water which is sprayed therein takes up an excessive amount of heat, so that the steam is raised to a high temperature before it leaves the boiler. The additional heat over and above that necessary to vaporize the water is carried away with the steam, and it is impossible to restore the heat at a sufficient rate to maintain the temperature necessary for water vaporization. Consequently the boiler ceases to operate after a few succes sive runs and is no longer effective as a source of steam for operation of the plant.

It is the object of the present invention to avoid the difiiculties experienced heretofore in the utilization of waste heat from the stack gases and to provide a method and apparatus whereby the heat may be utilized to produce steam and may be conserved so as to maintain uniform operation and production of steam. The invention affords a simple and effective solution of the problem of providing steam for water gas sets and renders unnecessary the provision of auxiliary boilers.

In carrying out the invention I provide a flash Usually it 'is neces-.

boiler through which the stack gases may be conveyed during the blowing period, heat absorbing surfaces being provided within the boiler to take up the heat from the gases and to store it during the interval of the blow period. After the commencement of the succeeding cycle, the gases are diverted from the boiler, and water is sprayed therein and coming in contact with the heated surfaces is converted into steam. The steam at high temperature is delivered to a heat transformer which is partially filled with water to a substantially constant level. The steam is distributed below the surface of the water, and the surplus heat is thus absorbed, converting a portion of the water into steam and raising the temperature of the remainder of the water to a substantial degree. The water thus initially heated is delivered during the proper interval to the flash boiler, and being already heated it is readily converted into steam which returns to the heat transformer as hereinbefore described. The steam in. the transformer, after giving up its excess heat to the water and being augmented by steam which is formed in the transformer, is delivered to the base of the generator and utilized in the manufacture of water gas.

The operation as described permits the production of steam in a sufficiently continuous manner and in suflicient volume to supply the generator. The invention affords a saving in cost of installing and maintaining boilers and the cost of fuel used therein, and utilizes also heat which otherwise would become a total loss in the process.

The invention will be more clearly understood by reference to the accompanying drawing, which illustrates more or less diagrammatically in elevation with parts in section an apparatus adapted for the practice of the invention, it being understood that details of the water gas set which are 95 well known to those skilled in the art are omitted for the purpose of clarity. The invention may be applied to water gas sets of differing design and construction, the operation of all such equipment being essentially the same.

Referring to the drawing, 5 indicates the water gas generator, 6 the carburetor, and '7 the superheater of a water gas set. It is to be understood that suitable provision is made for the introduc- 5 tion of carbonaceous fuel, as for example through charging hole 41, to the generator and for the introduction of carburetting material to the carburetor. The carburetting material may be introduced through oil inlet 42. Likewise, the ap- 110 paratus is equipped to permit the introduction of the necessary air to the generator.

During the blow period air alone is introduced at the bottom of the generator thus forming producer gas which is burnt in the carburetor, and superheater. The waste gases pass to the top of the latter, and in the absencefof 'a waste heat boiler or a flash boiler are discharged through a stack cap 8.

In accordance with the present invention, the

with sufficient strength to withstand the pressure of the steam generated therein. The boiler is provided with a plurality of heat absorbing surfaces 11, preferably of refractory material, so disposed as to permit the circulation of the-gas thereabout and the absorption of heat therefrom. The gas escapes from the top of the boiler through an outlet which may be closed by a cover 12,. The boiler 'may be provided with an opening at its bottom, normally. closed by a cover 13, to permit the withdrawal of accumulations of finely di-.

# vided solid material which is carried along with the gas and separated in the boiler.

At the commencement of the steam run period,

the. water gas produced in the generator by the reaction of steam on the fuel bed is passed into the carburetor, where it is enriched with oil or other enriching medium introduced through 42. The carburetted water gas thus produced is passed through the carburetor and superheater 7 into washbox 44. During adownrun water gas.

ratus- (not shown).

- making cycle, water gas produced-in the generator by the reaction of steam on the hot vfuel bed is withdrawn through pipe 45, which leads into the washbox 44. From the washbox, the gas may pass to a holder'or suitable gas purification appa-- Simultaneously with the passage of steam'through the fuel bed, wateris introduced through a pipe 14 and'directed by spray nozzles 15 onto the heated surfaces within the boiler. The steam is withdrawn through a pipe 16 and'is delivered thereby to a distributor 17 having openings 18 in the bottom thereof. The distributor may be generally cylindrical, in form and is disposed within a heat transformer l9 also of cylindrical form and constructed with sufficient strength to resist the pressure of the steam developed. The openings in the distributor 17 are disposed beneath the level of the water which is maintained in the transformer, the level being kept constant by means of a valve 20 controlled by a float 21, the valve beingv disposed in 5 temperature of the water in the heat transformer is raised, and the heat carried from the boiler is thus conserved. The steam from the heat transformer is delivered through a pipe 24 to the generator 5 and is utilized therein forthe purpose of the operation. r

The water which is heated in the heat transformer 19 may be delivered through a pipe-25 and strainer 26 to a circulating pump 27 which returns it through a pipe 28 to the pipe 14. Additional water may be'supplied to'the pipe "which is carried away with the steam is promptly returned to the boiler in the preheated water. blow gas is delivered from the superheater 7 through a pipe 9 to a flash boiler 10 which may be generally cylindrical in form and constructed" The operation of the apparatus as hereinbefore described does not interfere with the normal operation of the water gas set, which follows the usual cycle including the air blow period during which the gases are delivered to the flash boiler for the purpose of heating the contact surfaces are diverted from the flash boiler and water is introduced thereto for the purpose of producing steam. Coincidently steam is introduced to the bottomof the generator to react with the carbonaceous fuel to produce water gas, and the lat-v ter is delivered through the carburetor and.super-. heater in the usual manner. If the water gas setis operated in two cycles, including a steam uprun and a steamback-run, the latter cycle may follow the up-run while water is still being supplied to the flash boiler for the purpose of producing steam. In theback-run the water may be supplied from the heat transformed to the superheater, or waterfrom any suitable source can be introduced thereto. It is also possible tov introduce steam from the. heat transformer tov the superheater through a suitable .connection provided for that purpose.

The method and apparatus as described afford a simple and economical arrangement whereby the steam required for the operation of the water gas set may be produced solely by the utilization of waste heat therefrom. It is adapted to plants of any size, but is particularly useful in connection with small plants or plants which are operated for only a portion of the time, because .it avoids the necessity. for the construction and maintenance of aseparate boiler plant for the production of steam.

I It is to be understood that in accordance with the usual practice the heat transformer and steam .and hot water pipes connected thereto should be thoroughly insulated to avoid heat losses. Similarly other details of construction in accordance with usual engineering practice in connection with water gas setsmay be utilized in applying the invention.

Various changes may be made in the details of construction and of arrangement of the plant without departing from the invention or sacrificing any of its advantages.

I claim:

1. In an apparatus for recovering waste heat from hot gases, the combination of a flash boiler including a surface adaptedto absorb heat from the gases, means for delivering the gases to the boiler and for supplying water thereto, means for maintaining a body of water, means for delivering. 1 steam produced in the boiler beneath the surface of the water'whereby surplus heat carried by the steam is conserved, and means for recirculating water which is not converted into steam by initial contact with the heated surface;

2. In an apparatus for recovering waste heat from hot gases, the combination of a flash boiler including a surface adapted to absorb heat from the gases, means for delivering the gases to the boiler and for supplying water thereto, means for maintaining a body of water, means for delivering steam produced in the boiler beneath the surface of the water whereby surplus heat carried by the steam is conserved, and means for delivering water from the said body to the boiler.

3. In an apparatus for recovering waste heat from hot gases, a water gas generator, means to supply air to a body of fuel maintained therein, a flash boiler including a surface adapted to absorb heat, means for delivering gases from the generator to the boiler, means for supplying water to the boiler, means for maintaining a body of water, means for delivering steam produced in the boiler beneath the surface of the water whereby surplus heat carried by the steam is conserved and means for conveying the steam to the generator.

4. In an apparatus for recovering waste heat from hot gases, a generator, means to supply air to a body of fuel maintained therein, a flash boiler including a surface adapted to absorb heat, means for delivering gases from the generator to the boiler, means for supplying water to the boiler, means for maintaining a body of water, means for delivering steam produced in the boiler beneath the surface of the water whereby surplus heat carried by the steam is conserved, means for conveying the steam to the generator, and means for recirculating water which is not converted into steam by initial contact with the heated surface.

5. In an apparatus for recovering waste heat from hot gases, a generator, means to supply air to a body of fuel maintained therein, a flash boiler including a surface adapted to absorb heat, means for delivering gases from the generator to the boiler, means for supplying water to the boiler, means for maintaining a body of water, means for delivering steam produced in the boiler beneath the surface of the water whereby surplus heat carried by the steam is conserved, means for conveying the steam to the generator, and means for delivering water from said body to the boiler.

6. In a carburetted water gas set comprising a generator, a carburetor and a superheater connected in series and operating with alternate air blasting and water gas making periods, a flash boiler including a surface adapted to absorb heat from the blast gases formed in the generator during the air blasting period, means for passing blast gases from the generator through the flash boiler, means for supplying water to the flash boiler during the water gas making periods, means for maintaining a body of water, means for delivering steam produced in the flash boiler beneath the surface of the body of water whereby surplus heat carried by the steam is conserved, means for conveying the steam to the generator during the water gas making periods, and means for delivering water from said body of Water to the flash boiler.

FRANK W. STEERE. 

